Beneficiation of ores



,pecially quartz and silicate minerals.

Patented Dec. 21, 1943 2.337.112; 'BENEFICIATION F onus John Frank Lontz, Wilmington, Del., assignor to I E. I. du Pont de Nemours & Company, Wilmington, DeL, a corporation of Delaware No Drawing. Application October 7, 1940, Serial No. 360,160

6 Claims. "(01. 209-166)- This invention relates to an improved process for the concentration of ores, more particularly it relates to a method for improving the efliciency of froth flotation processes employing cationic surface active compounds as flotation agents. Still more particularly it relates to the use of assisting agents in froth flotation processes employing cationic surface active compounds as flotation agents; and still more particularly it relates to the use of assisting agents comprising Water soluble open chain aliphatic carboxylic acids containing not more than nine carbon atoms, and their water-soluble salts and amides in froth flotation processes for the concentration of negatively-charged minerals employing cationic surface active compounds as flotation agents.

This invention has as an object the development of an improved method for separating or concentrating neg'atively'charged minerals es- A further object is to increase the selectivity of cationic surface active compounds as flotation agents in such processes by using in combination with such agents water-soluble open chain aliphatic carboxyiic acids containing not more than nine carbon atoms and water-soluble salts and amides of such acids. A still further object is the production of an improved process of concentrating metal carbonate and oxide minerals, using cationic surface active agents as flotation agents and an agent selected from the class of water-soluble open chain aliphatic, carboxylic acids containing not more than nine carbon atoms and water-soluble salts and amides of such acids as an assistant. Other objects will appear hereinafter.

The anove and other objects appearing hereinafter are'accomplished by the following invention which comprises adding to a plup containing metal carbonate and/or oxide minerals and negatively charged gangue material a cationic surface active compound as a flotation agent and an agent selected from the class of watersoluble open chain aliphatic carboxylic acids containing not more than nine carbonatoms and water-soluble salts and amides of such acids as an assisting agent, and subjecting the same to a flotation operation. The valuable fraction of the ore may be found in the froth layer or it may remain in the cell. In this way a sharper separation of valuable mineral from gangue is efl'ected, resulting in a purer product and greater recovery.

The ability of cationic surface-active reagents to fioat siliceous minerals by means of a froth in preference to the indifferent metallic oxides and carbonates has been utilized by this invention, but the performance of the cationic surface active compounds as flotation agents has been improved, particularly in the separation of siliceous material from calcium carbonate, or limestone, by the use of water-soluble open chain aliphatic carboxylic acids containing not more than nine carbon atoms and their water-soluble salts and amides as added assistants. These assistants have been found to promote separation of more of the siliceous material for a given amount of flotation agent resulting in the separation of a higher grade of limestone with the same or higher recovery remaining behind as tailings. For example, when citric acid is added as an assistant (Example V) to a flotation operation using crude dodecylamine hydrochloride, the grade of CaCOa from the flotation operation is improved from 85.82 to 94.9 witha recovery increase from 81.2% to 87%. Another way of expressing the same effect is to state that in the majority of cases for the production of a desired grade of mineral concentrate a substantial reduction in the required amount of collector is made possible by the addition of an assistant. In certain instances an improvement in the collecting power of cationic surface active compounds results from leaching the ore with a small amount of a mineral acid such as hydrochloric acid prior to the flotation step.

This invention will be further illustrated but is not intended to be limited by the following examples: EXAMPLE I I A sample of siliceous limestone used in the production of Portland cement was employed in flotation experiments using assistants with cationic surface active compounds as flotation re grinding 1 kg. of the minus 40-mesh ore for 70' minutes in a one-gallon porcelain jar mill with one liter of water and 3 kg. of flint pebbles. The ore particles were then about 84-86% minus 200- mesh.

- drochloride was added. Fifty-five thousandths of a gram of the frother hereafter referred to as frother b, was added to induce frothing. The frothing agent consisted of the branched-chain, oxygenated organic compounds prepared by the catalytic hydrogenation of carbonv oxides under elevated temperatures and pressures as described in U. S. Patents 1,844,129,1,844,857, and 1,939,708. The boiling range of the particular fraction of these ongenated organic compounds used was 147-157 C.

With the'addition of frother b a heavily loaded froth, dark gray in color, formed rapidly and was collected for 9 minutes, after which time there was no further collection of minerals or production of froth. The flotation concentrate and tailings were filtered, dried, weighed. and

analyzed for their calcium carbonate content. The results are summarized in the following magenta-Crude dodecylamine hydrochloride 0.05 g. or 0.10 lb./ton. Frother b, 0.055 g. or 0.11 lb./ton.

It will be noted from the table that 81.2% of l the calcium carbonate remained in the cell in the underflow," commonly called the tailings" in ore dressing terminology. Since the desired mineral concentrated in the underflow, I prefer not to use the term "tailings as that term generally implies a waste product or gangue. Similarly I have used the term overflow to designate the product carried out of the cell by the froth. Generally, the product frothed out of the cell is called the "concentrate but I prefer to avoid that term, since in its usual use it connotes a purification or segregation of valuable minerals and in my process the froth carries out the undesired minerals. The terms underflow.and "overflow" are therefore used to designate my improvement has been made by the addition of hydroxyacetic acid as indicated by the substantial increase in the grade of limestone, represented by the underflow, from 85.82% to 91.15% of calcium carbonate in addition to an increase in recovery from 81.2% to.85.8%.

EXAMPLE III Weight CaCl; Per cent Product g Per cent weigh t recovery Heads 1, 000. 0 l 74. 2 742. 3 Overflow 306. 0 37. 70 115. 3 15. 6 Underflow 694. 0 90. 34 627. 0 84. 5

l Calcd.

Magenta-Crude dodecylamine hydrochloride, 0.05 g. or 0.10 lb./ton. Frother b, 0.055 g. or0.l1 lb./ton. Levuiinic acid 0.10 g. or 0.20 lb./ton.

The addition of levulinic acid increased the grade of underflow from 85.82% obtained by the control run, to 90.34% calcium carbonate with an increase in recovery from 81.2% to 84.5%.

EXAMPLE IV A number of assisting reagents in addition to those described in Examples 112 and III were tested under the same conditions outlined in the control run (Example I) using 0.05 lb./ton crude dodecylamine hydrochloride and 0.14 1b./ton

flotation products rather than the commonly used terms "tailings and concentrate. In the above experiment the grade of limestone was increased from 81.0% to 85.82% of calcium'carbonate with a recovery of 81.2%.

By crude dodecylamine hydrochloride as used herein is meantthe mixture of hydrochlorides of Y the higher primary aliphatic amines in which the allwl groups correspond in carbon content and composition to the fatty acids occurring naturally in coconut oil.

Exeuru: II

The process of Example I was repeated using, in addition to the same quantities of crude dodecylamine hydrochloride and frother b, 0.35 gram of hydroxyacetic acid. The flotation fractions were filtered, dried, weighed and analyzed as before. The results of this experiment using hydroxyacetic acid as an assistant are summarized in the following table:

Rwanda-Crude dodecylamine hydrochloride, 0.05 g., or 0.10 lb./ton, Frother b 0.055 g. or 0.11 1b.lton. Hydroxyacetic acid 0.35 g. or 0.70 lb./ton.

Comparison of the above results with those of the control run (Example I) shows that a marked frother b. For sake of brevity, typical results are listed in the accompanying table:

The above variations in the analyses of the heads are due to the different batches of limestone used for the tests.

Exam-ta V The process of Example I was repeated with the addition of 0.10 g. or 0.20 lb./ton of citric acid as an assistant. The flotation fractions were filtered, dried, weighed and analyzed as before. The results are summarized in the following table:

C8C0s Product Weight Percent Weight recovery Heads 992.5 78.7 780.7 0verfl0w 276. 5 36. 8 101. 2 13.0 Underflow V 716.0 94.9 679.5 87.0

Calcd.

Reagmts: Crude dodecylamine hydrochloride, 0.05 g. or 0.l0.lb./ ton. Frother b, 0.055 g. or 0.11 lb./ton Citric acid 0.10 g. or 0.20 lb./tou

Exemrta VI The process of Example I was repeated with the same reagents but with 0.10 g. of tartaric acid as an assistant. The flotation fractions.-

were filtered. dried, weighedand analyzed as Reaqents.-Crude dodecylamine hydrochloride, 0.05 g. or 0.10 Frotber b, 0.055 g. or 0.11 lb./ton tartaric acid 0.10 g. or 0.20

It 'is apparent that the addition of tartaric acid increases the amount of overilow as compared with the control run in Example I. The grade of the underflow was increased from 85.82 to 90.7% calcium carbonate with an increase in recovery from 81.2% to 90.6%.

Exunns VII.-Control A slurry of 100 g. of Minnesota iron ore washer tailings was treated with 0.015 g. crude dodecylamine hydrochloride and 0.009 g. frother b. The resulting froth was collected for 6 minutes, broken down with a mixer and then recleaned with 0.003 g. crude dodecylamine hydrochloride and 0.009 g. frother b. The fractions were filtered, dried, weighed and analyzed for the hydrochloric acid soluble content, which is a measure of iron content. The results are tabulated below:

Reagents rougher opemlion.0.30 lb./ton crude dodecylamlne hydrochloride. 0.18 lb./ton irother b.

Cleaner operation.0.06 lb./ton crude dodecylamine hydrochloride.

0.18 lb./ton irothcr b.

In repeating the above process using crotonic acid to the extent of 0.20 lb./ton in the rougher operation, the higher hydrochloric acid-soluble content in the underflow is increased and at the same time the silica rejection is higher, thus giving an iron concentrate of higher quality.

In place of the water soluble carboxylic acids containing not more than nine carbon atoms listed in the above examples, others may be substituted with equally good results. Additional suitable agents include formic, amino-caproic, gluconic, aminobutyric, chloracetic, lactic, pyruvic, malonic, tartronic, malic, aconitic, and adipic acids. In place of the free acids, their watersoluble salts, e. g. the alkali metal, amine and ammonium salts, as well as their water-soluble amides may be used. Methyl, ethyl, propyl, isopropyl and butyl amines are useful as salt forming components. Examples of amides operable in the practice of the invention include formalnide, N-p-hydroxyethyl formamide, N-bis(phydroxyethyl) -propionamide, and N,N -bismethylol adipamide. If desired, mixtures of one or more of the above assistants may be used.

In addition to the specific cationic surface active agents disclosed in the examples, we have found that a very large number of other agents of this type will give good results. Either single compounds or mixtures are useful. Among the agents which can be used to advantage in the separation of metal carbonates and oxides from siliceous gangues, the following may be mentioned:

Hexadecyl trimethyl ammonium bromide or chlo- Dodecyl trimethyl ammonium bromide or chloride Octadecyl trimethyl ammonium bromide or chloride Hexadecyl pyridinium bromide or chloride Dodecyl pyridinium bromide or chloride Dodecylamine hydrochloride, hydrobromide, ni-

trate, acetate or chloroacetate Hexadecylamine hydrochloride Octadecylamine hydrochloride Dodecyl dimethyl sulfonium methyl sulfate Dodecyl dimethyl sulfonium bromide Octadecyl methyl ethyl sulphonium iodide Tetradecyl dimethyl sulphonium bromide Dodecyl methyl cyclohexyl sulphonium iodide Dodecyl benzyl methyl sulphonium chloride 1 A large list of useful ammonium, sulphonium and phosphonium compounds which have'utility are set forth in Dunbar U. S. Patent 2,165,356.

The agents of our invention may be designated by the following general formula:

in which R is a non-aromatic (i. e. non-benzenoid) hydrocarbon radical of 8 to 22 carbon atoms; M represents pentavalent nitrogen, pentavalent sulfur or tetravalent sulfur; R represents hydrogen atoms or hydrocarbon radicals having not more than 5 carbon atoms which may be constituents of an alicyclic or of a heterocyclic ring; :c is an integer less by two than the valence of element M, and Y is a negatively charged salt forming radical, i. e.. atom or group, for example, chlorine, bromine, nitrate, acetate, chloroacetate, etc. The long chain aliphatic radical R need not be entirely composed of carbon atoms in the chain but may contain ether linkages, ester groups, sulfur atoms, carbonyl groups, etc. provided these groups do not introduce new centers of polarity.

For example, reagents such as the hydrochloride of the dodecyl ester of alpha-amino-isobutyric acid, the hydrochloride of beta-aminoethyl dodecyl ether, and the hydrochloride of the dodecyl ester of alpha-amino-isobutyric acid are good flotation reagents for use in the process of this invention; such substances, however, as the hydrochloride 0f along chain amine having a carboxyl group on the end removed from the amino group would not produce the desired effect, since another polar. solubilizing group has been introduced.

Two other types of cationic surface-active reagents which bear some mention are found useful in the practice of this invention. One of these types comprises salts of amino naphthenes derived from naphthenic acids of 12 to 20 carbon atoms and natural acidic resins, e. g. rosin, Congo, kauri, Manila, sandarac, damar, pontianac, Zanzibar, etc. The aminonaphthenes can be made by catalytically dehydrating the acids in .the presence of ammonia and subsequent reduction of the nitriles to the corresponding amines and the salts can be made by treating the amines with an acid, e. g. hydrochloric. The reactions involved are discussed below in connection with higher fatty acids.

The second class which appears to differ from the type formula are the betaines having long aliphatic chains. some illustrative betaine type compounds apparently have the following formula, although there is some evidence in favor of their being noncyclic compounds:

CHI

R- CH2III 1:6. Ordinarily a neutral pulp is used, but in some cases it may be desirable to use an alkaline or acid pulp.

It will be clear from the above that one of the uses of this invention is the preparation of cal cium carbonate of good quality from natural rocks whose calcium carbonate content is too low to be of technical value. By means of this process limestone rocks containing 40-70% cal- 0 cium carbonate can be purified to such an extent The betaines are particularly effective if used 2 COOH ' A class of substances which we have found to be particularly effective is .composed of mixtures of salts of amines derived from the fatty acids obtained by hydrolytic splitting of natural fatty glycerides, e. g. palm oil, coconut oil, stearin, etc.

For example, the mixtures of amines derived from coconut oil fatty acids by the following series of reactions such as follows gives excellent flotation results after conversion to a watersoluble salt such as the hydrochloride oracetate.

The amount of cationic surface active compounds required to produce the above effects varies somewhat with the reagent chosen and the particular ore being treated. In general, the amount needed will be between 0.05 and 2.0 pounds per ton of ore, but in some cases somewhat smaller or larger quantities may be re-' quired. The amount of water-soluble open chain aliphatic carboxylic acid or water-soluble salt or amide used may also vary widely, in general from 0.01 pound to 5.0 pounds per ton of ore is satisfactory. In most instances,-however, from 0.2 to 1.0 lb./ton is sufficient. Some of the reagents produce suificient frothing so that an additional frothing agent is not required, while others have little or no frothing power. When greater frothing power is needed, we prefer to use a material such as pine oil, cresylic acid or frother b, since these frothers have no adverse effect on the selectivity of the collecting agents. Occasionally we find it advantageous to use mixtures of two or more of the cation-active reagents to produce flotation products of high quality. In carrying out a flotation process according to the teachings of this invention, any of the well known types of flotation cells may be employed. The ratio of pulp solids to water may vary from about 1:1 to

1.1 by this process.

also permits the recovery of iron carbonate,

that the product can be used in-the manufacture of Portland cement. It is also possible to prepare calcium carbonate concentrates approaching theoretical purity from low-grade limestone The process of this invention managanese carbonate, magnesium carbonate, and other metallic carbonates from ores contaming these minerals with other siliceous materials as impurities.' Conversely it may be used to prepare talc, mica, or quartz products of high purity and value when the principal impurities are alkaline earth or heavy metal carbonates or oxides. While the herein disclosed examples apply to the use of assistants in the beneficiation of calcium carbonate, the same principles apply to the concentration of oxidized iron minerals in which the cationic surface active collectors are benefited through the use of the protective colloid assistants of the carbohydrate type.

The present process affords two outstanding advantages as compared with previously known methods for the removal of siliceous minerals by means of cationic surface active agents as collectors. First, it provides a process by which quartz and siliceous minerals including iron ores, as disclosed in the preceding paragraph can be A separated from other minerals at a substantial reduction in the amount of collector through the use of assistants. Secondly, with a given amount of cationic surface-active agents, the use of an asslstantincreases the selectivity as a result of which a higher grade of mineral concentrate is obtained.

While the preferred embodiments of our invention have been disclosed, it will be readily apparent to those skilled in the art that many variations and modifications may be made therein without departing from the spirit of the invention.

I claim:

1. In a froth flotation process for concentrating negatively charged minerals which involves incorporating in an aqueous pulp of ores containing such minerals a cationic surface active agent having a long chain aliphatic hydrocarbon radical of 8-22 carbon'atoms and a negatively charged salt forming radical, the step which comprises adding to the pulp a separate assistant taken from the group consisting of water soluble open chain aliphatic'carboxylic acids containing not more than 9 carbon atoms and their water soluble salts and amides.

2. In a froth flotation process for concentrating ores containing negatively charged minerals and minerals taken from the group consisting of metal carbonates and oxides which involves incorporating in an aqueous pulp of such ores a cationic surface active agent having a long chain aliphatic hydrocarbon radical of 8-22 carbon atoms and a negatively charged salt forming radical, the step which comprises adding to the pulp a separate assistant taken from the group consisting of water soluble open chain aliphatic carboxylic acids containing not more than 9 carof metal carbonates and oxides which involves incorporating in an aqueous pulp of such ores a cationic surface active agent comprising a wa-' 5. In a froth flotation process for concentratingores containing negatively charged minerals and minerals taken from the group consisting of metal carbonates and oxides which involves incorporating in an aqueous pulp of such ores a cationic surface active agent comprising a water soluble dodecyl amine salt, the step which combie open chain aliphatic carboxylic acids containing not more than 9 carbon atoms and their water soluble salts and amides. v

4. In a froth flotation process for concentrating ores containing negatively charged minerals and minerals taken from the group consisting of metal carbonates and oxides which involves prises adding to the pulp the water soluble amides of open chain aliphatic carboxyiic acids containing not more. than 9 carbon atoms in an amount from 0.1 to 5.0 pounds per ton of ore, said surface active agent being used in an amount between 0.05 and 2.0 pounds per ton of ore.

' -6. In a froth flotation process for concentrating ores containing negatively charged minerals and minerals taken from the group consisting of metal carbonates and oxides which involves incorporating in an aqueous pulp of such ores a cationic surface active agent comprising a water soluble dodecyl amine salt, the step which comprises adding to the pulp the water soluble salts of open chain aliphatic carboxylic acids containing not more than 9 carbon atoms in an 

